Obstetrical forceps are medical instruments comprised of two blades (i.e. the fetal head engaging portions), each connected to a handle by a shank, with a sliding lock between the handle and the shank. The forceps typically grasp the fetal head in a tong-like manner and are used for assisting in the delivery of a baby. When needed, they can be a valuable medical tool to shorten or end the second (expulsion of the fetus) stage of labor, whenever to do so is in the best interest of the mother or the fetus.
In 1925 A. H. Bill introduced the axis-traction handle for the obstetrical forceps, which was widely accepted and soon became an integral part of the instrumental delivery armamentarium available in every delivery room.
The Bill axis-traction handle consists of a claw, which is applied to the forceps handle finger guards just like two fingers would grasp them, a vertical rod connecting, through a movable joint, the claw to a horizontal traction rod, which, in turn is attached to a handle grip. The purpose of the Bill axis-traction handle is to increase the accuracy of traction, i.e., to allow the physician to direct the traction away from the symphysis into the axis of the pelvis, which is the one of least resistance, thus, reducing the amount of traction necessary for a forceps delivery.
Regrettably, even when the axis-traction principle is strictly adhered to, the possibility of maternal and/or fetal injury, secondary to excessive pull, remains a reality. In fact, when to desist from further extractive efforts is left to the judgment and courage of the obstetrician.
To be sure, the medical literature contains several reports of attempts made to modify the Bill axis-traction handle in order to be able to measure the pull applied during a forceps delivery, and thus, reduce the risk of injury to the fetus. As early as 1935, B. Wylie reported a modification of the Bill axis-traction handle with the insertion of a spring mechanism to measure the amount of traction during a delivery. A similar spring mechanism was described in 1946 by J. Baxter. In 1959 A. R. Fleming et al. reported a further modification consisting in the placement of strain gauges on the vertical rod of the handle, connected to a recording instrument.
The above modifications, while useful for research purposes, have not, however, gained clinical acceptance, possibly because they require calibration, have cumbersome cable connections, and pose problems with sterilization.
Accordingly, there is a need for an improved axis-traction handle for the obstetrical forceps, that can measure the pull exerted on the handle, and thus on the fetal head, during a forceps delivery, without the constraints and design drawbacks seen in the prior art and described above.